Current trends in heterogeneous catalysis research as well as in material sciences and related sciences have led to an increased drive to apply known characterisation techniques, such as powder X-ray diffraction, under elevated temperatures, pressures and changing gas and/or liquid atmospheres. Commercially available in-situ X-ray diffraction chambers (for example those produced by the Austrian company Anton-Paar) do facilitate the study of materials at elevated temperatures (up to 900° C.), pressures (up to 10 bar) and under different gas atmospheres.
However, their design entails a fairly large volume reaction chamber (approx. 500 ml) into which the sample is inserted on a plate-like sample holder. The most well known example known to applicant in their range is a model known as XRK. A large volume reaction chamber of this nature does not allow for a rapid changeover of gasses fed to the reaction chamber. As a result, an appreciable period of time elapses when the gas composition in the feed is changed before the reaction to the change can be studied. Secondly, those reaction chambers are provided with beryllium (category 1 carcinogen) or similar X-ray invisible windows that limit the temperatures and pressures that can be applied to the reaction chamber. Thirdly, they are unable to accommodate liquid products and/or corrosive or oxidising gasses and vapours such as water either in the feed or in the reaction products stream such as would occur in a fixed bed reactor system. These cells are thus generally limited to dry conditions that do not result in corrosion.
The bulky design of the reactor chamber and the plate-like sample holder further does not allow a realistic plug flow like flow pattern through the powder sample due to the presence of dead volumes and poorly defined concentration gradients. This does not allow the determination of kinetic information in, for example catalyst testing, and always leaves a doubt whether the chosen conditions do actually represent the conditions in real live applications.
A sample presentation device using a glass capillary as the reaction chamber has been proposed in French patent number FR2856793 that, as far as applicant is aware, has not yet been made commercially available. The capillary has an electrical heating element carried in a sleeve that substantially surrounds the capillary tube and a thermocouple associated with that sleeve is employed to measure the temperature of the sleeve from which the temperature within the capillary reaction chamber is inferred. The temperature range is stated to be up to 250° C. with a pressure range up to 5 bars. An important feature of the device described is that the reaction chamber can be oscillated about its own axis in order to better present the sample within the capillary reaction chamber to the X-radiation. As far as applicant is concerned the device described does not fulfill requirements and also has shortcomings in its range of operation. No particular mention is made of liquids or vapours in the feed or product streams.
Synchrotron based applications rely on capillaries much more as reaction vessels and plug flow reactors for studies in catalysis, biology and material sciences. However the small number of synchrotron facilities available worldwide and their enormity in size and cost render the use of a synchrotron out of the reach of, and generally unavailable to, the majority of researchers and small-scale facilities. Laboratory powder X-ray diffractometers are, on the other hand, wide spread and are commonly available and frequently used in modern research and other facilities. It is also noted that, as far as the applicant is aware, synchrotrons typically employ a hot air gun to effect heating of the sample which is a technique that is unsuitable for laboratory equipment.
Applicant believes that there is a need to provide a sample presentation device for radiation-based analytical equipment that is simple, cost effective, and yet has practical operating ranges.
Applicant also believes that there is a need to provide a sample presentation device for radiation-based analytical equipment that is able to accommodate liquids and vapours in the feed and product streams.